Met police director says live facial recognition beats accuracy expectation

The experience of UK police with live facial recognition is poorly understood, and the technology is proving more effective than people realize, says Metropolitan Police Director of Intelligence and facial recognition lead for the National Police Chiefs’ Council Lindsey Chiswick.

UK police use NEC’s facial recognition algorithm, which is exceeding the accuracy expectations of the Met Police, reports Policing Insight.

The Met Police deployed LFR eight times within the first two months of the year in Croydon, resulting in 64 arrests. The same number of officers would have made far fewer arrests without the technology, Chiswick says. She previously shared more arrest figures from across England, just as Islington was joining Haringey and Newham as the third borough to reject a Met deployment of LFR. Policing Insight reports in a separate article that LFR has been deployed 115 times since 2017 by South Wales Police and 105 times since 2020 by the Met Police. Out of 1.28 million faces compared, resulting in 561 arrests “or other disposals.”

Chiswick argues that facial recognition benefits the broader public beyond just improving the effectiveness and efficiency of law enforcement.

“The real plus point – which I think we sometimes miss and certainly the media does – is that all those other people are allowed to go peacefully on their way,” Chiswick tells Policing Insight.

“They’re not stopped, they’re not in any way interfered with. There’s a fleeting engagement of a face [with LFR] which is immediately deleted if you’re not wanted.”

Testing by the UK’s National Physical Laboratory (NPL) suggested the Met would have a false alert rate of about 1 in 6,000 when the threshold is set at the default 0.6, based on the NEC algorithm and the size of the Met’s watchlist.

The NPL tested the same algorithm at both higher and lower confidence levels. At a 0.64 threshold, the algorithm did not return any false positives. At 0.58 and 0.56, NPL observed higher levels of false positives, including evidence of racial disparities, with Black people incorrectly suggested as possible matches more often than people of other ethnicities.

South Wales police usually use a 0.62 threshold, according to the report.

There is no law or formal policy requiring a certain threshold, however, and Chiswick suggests that in some emergency situations, like an ongoing terrorist attack, lower thresholds could be used to increase the chances of a positive match.

Chiswick notes that NIST’s testing is helpful, but limited, as it does not include operational scenarios. That means most of the data UK police have on the accuracy of live facial recognition in operational settings comes from their own experience.

“At the start, the algorithms maybe weren’t as good as they are now,” Chiswick says. “But, as it’s improved and we get better at using it from a tactical point of view, then crikey, it really is precise, efficient and effective now.”

The frontline police officers who respond to alerts receive special training with NEC, and the force has several experienced LFR operators, at least one of whom is present at every deployment to ensure that camera angles and other important variables are carefully managed. Operational deployments also use a “blue list” to watch for a particular police officer working in the area, to check regularly that the system is still working properly.

Chiswick also pushes back on the notion that the technology’s use is unregulated. While not addressed in legislation specific to facial recognition or biometrics, she points out that the Human Rights Act, the Equality Act, the Data Protection Act and guidance from the ICO and Biometrics and Surveillance Camera Commissioner is added to College of Policing and force-level policy. “And I think there is a legislative framework already for me to operate under as a law enforcement body. Whether or not there needs to be [a single] law, I think I’ll leave to the lawmakers to decide.”

The day before the interview with Chiswick was published, the College of Policing published a list of five things people need to know about live facial recognition. Written by Inspector Karl Roberts of South Wales Police, the list briefly covers what LFR is, how it is used, how the technology works, the legal landscape, and which police forces use LFR.

Article Topics

accuracy  |  biometric identification  |  biometrics  |  facial recognition  |  London Metropolitan Police  |  NEC  |  NeoFace  |  police  |  real-time biometrics  |  UK